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Java > Open Source Codes > org > apache > tapestry > binding > StateBinding


1 // Copyright 2005 The Apache Software Foundation
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 package org.apache.tapestry.binding;
16
17 import org.apache.hivemind.ApplicationRuntimeException;
18 import org.apache.hivemind.Location;
19 import org.apache.hivemind.util.Defense;
20 import org.apache.tapestry.coerce.ValueConverter;
21 import org.apache.tapestry.engine.state.ApplicationStateManager;
22
23 /**
24  * Binding used to efficiently query whether an application state object (visit, global and friends)
25  * exists without actually creating it (or creating a session).
26  *
27  * @author Howard M. Lewis Ship
28  * @since 4.0
29  */
30 public class StateBinding extends AbstractBinding
31 {
32     private ApplicationStateManager _applicationStateManager;
33
34     private String JavaDoc _objectName;
35
36     public StateBinding(String JavaDoc description, ValueConverter valueConverter, Location location,
37             ApplicationStateManager applicationStateManager, String JavaDoc objectName)
38     {
39         super(description, valueConverter, location);
40
41         Defense.notNull(applicationStateManager, "applicationStateManager");
42         Defense.notNull(objectName, "objectName");
43
44         _applicationStateManager = applicationStateManager;
45         _objectName = objectName;
46     }
47
48     public Object JavaDoc getObject()
49     {
50         try
51         {
52             boolean exists = _applicationStateManager.exists(_objectName);
53
54             return exists ? Boolean.TRUE : Boolean.FALSE;
55         }
56         catch (Exception JavaDoc ex)
57         {
58             throw new ApplicationRuntimeException(ex.getMessage(), getLocation(), ex);
59         }
60     }
61 }
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